Kıyı çizgisine nehir birleşmesi durumu için kıyı çizgisi değişiminin numerik bir modelle incelenmesi
Analysis of development of a shoreline with the effect of a river
- Tez No: 66863
- Danışmanlar: PROF. DR. SEDAT KAPDAŞLI
- Tez Türü: Yüksek Lisans
- Konular: İnşaat Mühendisliği, Civil Engineering
- Anahtar Kelimeler: Kıyı şeridi, Nehirler, Sonlu farklar yöntemi, Coastal line, Rivers, Finite differences method
- Yıl: 1997
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: İnşaat Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Su Mühendisliği Bilim Dalı
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Kıyı Çizgisinin dengesini bozucu birçok etkenden dolayı kıyı çizgisi sürekli değişime uğramaktadır. Kıyı çizgisi değişimi, Pelnard Considere'nin geliştirdiği Tek Çizgi Modeli kullanılarak incelenmektedir. Kıyı çizgisine nehir birleşmesi durumunun incelendiği bu çalışmada;kıyı çizgisi değişimini explicit sonlu fark metodu ile hesaplayan Hanson ve Kraus'un Fortran 77 programlama dili ile yazılmış bilgisayar programından yola çıkılarak geliştirilen Basic programdan faydalanılmıştır. Nümerik model herhangibir özel bölge için değil.genel olarak araştırılmıştır.Bu sebeple programın girdileri verilirken dalga özellikleri.kıyı çizgisinin özellikleri ve kıyıya birleşen nehirin özellikleri gerçeğe yakın olarak verilmeye çalışılmıştır. Program gerçek veriler olmadan çalıştırılmasına rağmen, matematik modelin fiziksel modele ters düşmemesi programın amacına ulaştığının göstergesidir. Programda kullanılan surf bölgesindeki kıyı boyu katı madde taşınımı q(i),CERC formülü ile hesaplanmıştır.Kıyı çizgisi için kullanılan.çözümünde explicit model kullanılan denklem, katı madde için süreklilik denklemidir.Sınır şartlan olarak kıyı çizgisinin ve nehirin başlangıç şartları kullanılmış ve kıyı çizgisinin başlangıç durumu y(i)=0 alınmıştır. Kıyı çizgisinin başlangıç durumunun y=0 dan farklı şekilde verilmesi sonuç diagramlarda yalnızca nümerik değişikliklere sebep olmuş bunun yanında diagramları formları aynen korunmuştur. Bu sonuç da programın çalışmasının kıyı çizgisinin başlangıç koordinatlarına bağlı olmadığını kanıtlamıştır. Programda değişik dalga açılan ve dalga yükseklikleri için nehirin kıyı şeridine birleşmesi durumu araştırılmış ve sonuçlar herbir adım için ayrı ayrı incelenmiştir.:Ayrıca incelenen her bir adım için o adımdaki değişikliklerin sistemin tamamına etkisi yorumlanmıştır. vııı
Özet (Çeviri)
SUMMARY ANALYSIS OF DEVELOPMENT OF A SHORELINE WITH THE EFFECT OF A RIVER The method of Pelnard Considere has one major strong feature; it makes a hand computation of coastal changes possible.lt can be used for both the accretion and also the erosion on the lee side of a coastal sediment obstruction. Application in such a case will yield a coastal profile that is a mirror image relative to the origin of those found for accretion. The assumptions made in order to get an equation of motion are at best,so restrictive that the approach is primitive.Wave height and direction variations along the coast,tidal influences.and many of the other more sophisticated points of the Bijker formula have had tobe neglected.The assumption about the angle of wave attack,<j)',being very small can be very crude.especially since the toe of the zone affected by longshore transport -where §' is measured -can be well outside the breaker zone. The inclusion of an arbitrary coastline profile as an initial condition-as opposed to the straight line used here -is difficult, if not impossible.This makes the modeling of many“real coasts'Yather arbitrary. Improvements in the interest of navigation pose a number of associated problems and their solutions in turn give rise to another problems which may be termed”side effects". Other problems,not related to navigation.also arise due to increased populations and associated activities along the coast; e.g the problem of deterioration of water quality. Coastal problems can be classified as ; 1. Those indirectly related to,or resulting from navigation or navigation improvements. 2. Those due to factors not directly traceable to navigation or to navigation improvements. Hydraulic modeling is aproblem solving technique that requires the development, construction.verification and testing of ascale model of a particular prototype situation.lt allows an investigator to study various aspects of prototype behaviour without observing and testing the prototype itself.Although IXa model might not reproduce all prototype phenomena,it must be designed to yield the the desired design decision parameters.Basically, models are used as aids in the planning process. In certain cases, model results may.within themselves, provide sufficient information on which to base certain decisions, in other cases.modeling may be only one step or a small part of the planning process necessary to make a decision or develop a design The scientists always wondered and tried to learn about the properties of the water.At the beginning of the researches,it was about the water properties but as years passed and experiments developped the basis of the research became more detailed The Scientists tested the wave properties and the reaction between water and soil.Estimating the mechanism of the development of a shoreline provides to understand the form of the shoreline in the future and of course to estimate the form of the shoreline is very important for the mankind. Longshore sediment transport, caused by the effects such as wind flows, shore currents, waves, tides etc. change the shoreline by the time. Longshore current formed by the refracted waves and the components of wave energy along with the shore generate transport varies with the respect to the wave steepness expressed by H/L, grain size and beach slope. One line model are of the numerical models used to determine the shoreline development is widely in use in the recent years. The Thesis is about the development of a shoreline with the river junction. Hanson & Kraus tried to determine the mechanism of a shoreline.They used the finite element method and generated a computer program in two different ways.. Explicit program. implicit program Both of the programming ways depends on the same logic but the solution procedure differs. In this study Explicit program is used The most important change in the original program and this version is about the seawall. In the original program the shoreline is tested with the effect of the seawall.The Seawall which has a definite length and a definite distance from the shore is considered. Using the basic principles of sand transport mechanism,the form of the shoreline is determined. On the other hand in this study the most important effect is about the river.The width,the meeting point of the river and the shore and the sand properties of the river are given.In this situation the next form of the shoreline is determined.In the numerical model the sediment transport and the shore line development are calculated in 84, 180 hours and 240 hours, but these times can easily be changed. All the directions and the heights of the waves can be easily changed and of couse these changes may cause lots of differences but the numerical model be said to be quite succesfull about calculating the development of the shoreline. The longshore sediment transport is directly effected by the wave height and the wave direction. As the total sediment trasport is the sum of the longshore sediment transport of the river; to minimize longshore sediment transport is a really effective way to show the effect of the river. According to this aim running the program with various datas showed the changes in the graphics. One of the important variables about the river is the width. The river is assumed to effect the shore line partially. It means the width and the effective length determine the zone where the shoreline is effected by the river. The changes of this zone changes the erosion size and the erosion shape of the sediment in the joint coordinates. In this study the sand transport ratio q(i) is calculated with CERC formula but as we do not have any experiments to determine the sand transport ratio of the river,r(i) is assumed to be ampirical and that caused total sand transport ratio to be indefinite. The most important advantage of the numerical models is to run the situation as much as possible by changing the datas but as we know in physical models it is too expensive to run the situation more than once. But also physical models use the original datas and original situation so the results are more realistic. So the important think is to use these two models together and by this way the most realistic results can be determined. So at the end it can be said that if we have used both hydraulic modelling and numerical modelling the results would be more acqurate.AII the wave heights.wave directions and effective zone could be easily measured and the sand transport ratio of the river could be easily determined in physical model and after determining these variables the numerical model would give the real solutions. The initial conditions are given belove;. At the beginning of the running time ; r(i)=0 in all shore line if t(i)=0 then r(i)=0. Except the effective zone, the effect of the river is negligible. XI. if x=0 and t=0 q(i)= and y(i)=0 And for the last condition; Sy. ifx=Oandt>0 then=f 8x <|)-Wave attacking angle After all conditions are determined then y can be calculated. In the program Hanson & Kraus also studied about the form of the shoreline the coordinates of the shoreline can be assumed circular or as if it is a free form line. In this study the shore line is assumed 2000 m. length straight line. Of course to consider the shoreline parallel to x axis provides to show all the developments clearly but on the other hand as the form of the initial conditions differs from the original shape. So we can not get accurate results. Numerical models has been applied in seven different steps: In the first part of the thesis to understand and command on the original program,the original datas and positions are used. In the second step ;the effect of the river was added to the program and the effect of the seawall is decreased step by step.The sand transport ratio of the river is assumed to be a constant value. In the following two steps the only changing variable is the sand transport ratio of the river.In Part 3 The sand transport ratio of the river changes with the sand transport ratio of the current. In Part 4 The sand transport ratio of the river is assumed to be a ampirical value. After determining the sand transport ratio of the river the total sand transport ratio must also be determined. In the first 4 steps the total sand transport ratio is the sum of the sand transport ratio of the river and the sand transport ratio of the current but in the fifth step the total sand transport ratio is the sand transport ratio of the current minus the sand transport ratio of the river.After running these two conditions the differences can easily be marked.ln these two parts,to generate the difference ;. if q(i)=c(i)-r(i) then it means the total sand transport ratio decreases.. If q(i)=c(i)+r(i) then it means the total sand transport ratio inreases. xuIn the last two steps the sand transport ratio of the river is calculated more detailed. Changing all the datas without only natural values proved that the model theoretically obeys the physical model but as the datas aren't accurate and determined with tests, the solutions can't be said to be true. Infact the aim of this study is to understand the mechanism of the program developped by Hanson & Kraus and to prove if the affect of the river can be joined to this program or not. At the end of the study it can be said that, although there is no data about the original situation the graphics are not so different from the physical model. At the end of the study it was seen that the four groups belove, effects the development of the shore line.. Wave heights. Wave direction. Effective zone of the river. Sediment transport ratio of the river. X1U
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Yüksek Lisans
Türkçe
1988
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